Many polymers, particularly synthetic elastomers, are produced for commercial consumption in a particulate-form such as pellets, granules, briquettes, pills, spheres, crumb, and the like, either by deliberately forming into various shaped particles, or as a natural result of various recovery and drying operations in the polymer production process. The particulate-form of a polymer is convenient and desirable for many purposes since such particles are more readily compounded with other polymers, such as elastomers with resins to make high impact resins, or dissolved in various monomers for use in graft copolymerizations, or more readily dissolved in oils to make high viscosity lubricating oils, and the like. The particle-form of a polymer is much more readily handled for such further uses than are large blocks of polymer, or sheet, or the like.
Unfortunately, the convenient-to-use particles of many polymers, particularly those exhibiting any elastomeric character, tend to stick together, to be tacky, to agglomerate, to exhibit "blocking", which is an undesired adhesion between touching particles such as occurs under moderate pressure during storage. Particularly, storage under somewhat elevated temperatures, and under pressures caused by stacking bales or packages of polymer, create conditions favorable for such agglomeration. If the particles of the polymers agglomerate, then it frequently becomes necessary to grind, crush, or otherwise masticate the mass in order to re-separate the particles or to again produce a utilizable particulate material. Such mechanical treatment is burdensome and undesirable because of inconvenience, added labor and time, cost, possible contamination of the elastomer, and possibly in some instances even degradation of some of the polymeric products due to the additional working, temperature, and the like.
Some attempts to ease the problem have applied a dusting agent such as carbon black, talc, zinc stearate, rice flour, chalk, magnesium oxide, infusorial earth, or the like, to the particles in an effort to counteract the natural tackiness or blockiness of the particulate-form polymers. All of these dusting agents, however, have some objectionable characteristics. For example, adding color to the natural polymer may be undesirable for some purposes. The dusting agents themselves may be objectionable for some end-uses, such as lube oils for modern engines which are subject to rigorous specifications and limitations as to contaminants which may adversely affect the performance of the lube oil or may add undesirable insolubles or residues. Silica powder and some grades of talc may possibly pose health hazards under some circumstances that will restrict their use. Stearate powders at levels to be anti-tacky may adversely affect polymer performance properties such as tack, adhesion, optical clarity, and the like.
Needed is an anti-blocking treatment for normally tacky particulate-form polymers that can be easily added, readily controlled, employed in relatively small amounts, and be noncontaminating for most end-uses, yet produce highly effective results.